The invention relates to a method of monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a compound of cells of an energy storage device, which consists of a series connection of the individual cells of the energy storage device, in which case an individual cell may consist of one cell or of parallel-connected cells. In particular, the invention relates to a compound of cells of an energy storage device in an onboard power supply system of a motor vehicle. The invention further relates to a cell group logic for monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a compound of cells of an energy storage device, particularly of an energy storage device in an onboard power supply system of a motor vehicle, as well as to a central logic for monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a compound of cells of an energy storage device by way of a cell group logic, particularly of an energy storage device in an onboard power supply system of a motor vehicle.
Energy storage devices constructed of individual cells, preferably energy storage devices constructed of double-layer capacitors, are increasingly used in the automobile field. For providing and storing energy, these double-layer capacitors have the advantage that they can provide high power for a short time period. In order to arrive at the supply voltage required in a motor vehicle, the individual double-layer capacitors have to be connected in series. The series-connected cells thereby form a compound of cells. For charging, for balancing the cell voltage, for detecting the undervoltage and overvoltage of individual cells, for maintaining the charge of the cells in the standing operation, for the charging and discharging or the charge reversal between the individual cells as well as for the diagnosis/monitoring of the individual cells, individual cells or groups of cells are connected with respective cell group logics, which can receive energy from or feed energy to a rail line connected with these logics, in order to charge or discharge the individual cells or groups of cells. In the following, it will be described that each cell group logic is connected with a group of cells in order to monitor and/or control or automatically control their voltage. Here, the term “group of cells” comprises also individual cells, so that a case is also described in which a cell group logic is connected to each individual cell of a cell compound of an energy storage device in order to monitor and/or to control or to automatically control its voltage.
So that the cell voltages of the individual cells or groups of cells do not diverge during the cyclical charging or discharging, it is known to monitor the cell group logics by means of a higher-ranking automatic control device, specifically a central logic, and to control it such that a uniform charging and/or discharging is achieved, whereby a long service life of the individual cells and thus of the entire cell compound can be reached. The cell group logics are normally connected with the central logic by way of a data line, so that a data communication can take place for ensuring the described function.
However, this data line results in increased wiring expenditures and therefore in an increased susceptibility to faults. For reducing the wiring expenditures and the susceptibility to faults, many different methods of also transmitting data by way of existing supply lines are known, particularly in the automobile field. For this purpose, data to be transmitted between electronic devices are generally modulated upon the supply voltage lines. However, because of the resulting voltage level difference especially in the sphere of monitoring the voltage of individual cells at a cell compound, such an approach is unsuitable because measuring results or reference voltage levels impressed onto the supply lines, which are used for charging or discharging the cell groups or individual cells, are hereby falsified.
German Patent Document DE 197 33 866 A1, in contrast, describes a method and a system improved with respect to the above for transmitting data in a motor vehicle, where a satellite station is supplied with power by a central station by way of a data transmission line used jointly for the data transmission and the power supply. Here, the data transmission does not lead to a readjustment of a generator, so that the average voltage on the data transmission line (quiescent voltage) is not changed. However, since also here the data signals to be transmitted are simply superimposed on the quiescent voltage of the data transmission line in the form of current pulses which, even in the case of a small quantity, because of the high (output) resistance of the generator, result in strong voltage pulses, which are therefore easily detectable on the receiver side and which, on the receiver side, can easily be demodulated in a reliable manner by a comparator or a window comparator, it is also not possible here to carry out a power supply, which simultaneously defines a reference voltage level, by way of the data transmission line used for the data transmission and the power supply.
Thus, by means of the existing methods and systems for the data transmission on supply lines, no reliable monitoring and/or controlling or automatic controlling of the voltage of individual cells in a cell compound of an energy storage device, particularly of an energy storage device in an onboard power supply system of a motor vehicle, can be carried out where the voltage is determined for each group of cells and the group of cells is charged and/or discharged as a function of the determined voltage, at which voltage each group of cells is connected with a cell group logic, and by way of each group of cells, the cell group voltage is determined and, in the cell group logic, is compared with a desired voltage applied to a direct-voltage line with respect to the ground, and the group of cells is charged and/or discharged as a function of the difference between the determined cell group voltage and the desired voltage by way of the direct-voltage line, because the desired voltage would be falsified because of the data transmission.
It is an object of the invention to indicate an improved method of monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a cell compound of an energy storage device, particularly an energy storage device in an onboard power supply system of a motor vehicle, whereby a data communication can take place by way of the supply line of the cell group logics (rail line). It is also an object of the invention to indicate a cell group logic suitable for this purpose as well as a central logic suitable for this purpose.
The method according to the invention for monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a cell compound of an energy storage device, particularly of an energy storage device in an onboard power supply system of a motor vehicle, the group of cells being connected with a cell group logic by way of a supply line by which the group of cells is charged or discharged, which cell group logic monitors and/or controls or automatically controls the voltage of the group of cells, the cell group logic for the charging or discharging of the group of cells taking energy from a rail line or feeding energy to a rail line, and a communication between the cell group logic and another cell group logic and/or a central logic taking place by way of the rail line, is characterized in that a data communication is carried out with voltage levels between an idle level situated at or above a maximal voltage level, up to which the cell group logic exchanges energy with the rail line for charging or discharging the group of cells, and a data level situated above the idle level.
The cell group logic according to the invention for monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a cell compound of an energy storage device, particularly an energy storage device in an onboard power supply system of a motor vehicle, the group of cells being connected with a cell group logic by way of a supply line by which the group of cells is charged or discharged, which cell group logic monitors and/or controls or automatically controls the voltage of the group of cells, the cell group logic for the charging or discharging of the group of cells taking energy from a rail line or feeding energy to a rail line, and a communication of the cell group logic and another cell group logic and/or a central logic taking place by way of a rail line, is characterized by a voltage comparator unit which carries out a data communication by way of the rail line when voltage levels between an idle level situated at or above a maximal voltage level, up to which the cell group logic exchanges energy with the rail line for charging or discharging the group of cells, and a data level situated above the idle level are applied to the rail line.
The central logic according to the invention for monitoring and/or controlling or automatically controlling the voltage of at least one group of cells in a cell compound of an energy storage device by way of a cell group logic, particularly an energy storage device in an onboard power supply system of a motor vehicle, the group of cells being connected with a cell group logic by way of a supply line by which the group of cells is charged or discharged, which cell group logic monitors and/or controls or automatically controls the voltage of the group of cells, the cell group logic for the charging or discharging of the group of cells taking energy from a rail line or feeding energy to a rail line, and a communication taking place between the cell group logic and another cell group logic and/or a central logic by way of a rail line is characterized by a voltage converter unit which carries out a data communication by way of the rail line in that voltage levels between an idle level situated at or above a maximal voltage level, up to which the cell group logic exchanges energy for charging or discharging the group of cells with the rail line, and a data level situated above the idle level are impressed upon the rail line.
The above-mentioned cell group is either an individual cell or a compound of several individual cells, the number of cells in the group of cells in each case being smaller than the entire cell compound. For reasons of cost and expenditures, it makes sense to combine several cells in a group of cells and to determine the data for a group of cells instead of each individual cell. Advantageously, the cells are double-layer capacitors. The method, the cell group logic and the central logic are, however, also suitable for any other type of energy storage device constructed of individual cells. The cell group logic advantageously is a unit which, in addition to the voltage comparator unit, also has a control unit for charging and/or discharging the cell or group of cells. The voltage applied to the cell or group of cells can be determined directly in the cell group logic or in the central logic. The voltage control or automatic control of the cells is advantageously used for maintaining the charge as well as for balancing the voltage of the individual cells. In the above-mentioned implementation of the cell group logic and of the central logic, the central logic can transmit commands to the cell group logic during the data communication because the central logic can impress certain voltage levels onto the rail line and the cell group logic can detect the voltage levels of the rail line. When a bidirectional data communication is desirable, a voltage converter unit for impressing certain voltage levels can naturally also be provided in the cell group logic, and a voltage comparator unit for detecting voltage levels can naturally also be provided in the central logic.
Thus in comparison to the known state of the art, the method according to the invention, the cell group logic according to the invention and the central logic according to the invention have the advantage that the rail line can be used for supplying the cell group logic with a reference voltage by way of which the cell group logic can also be supplied with power, as well as for a data communication between the central logic and the cell group logic without interfering with the reference voltage. According to the invention, this takes place in that the data communication takes place by means of voltage levels which are above the maximal voltage level, up to which the cell group logic exchanges energy with the rail line for charging or discharging the cell group; that is, up to which the rail line is used for “transmitting” the reference voltage. When the maximal voltage level is exceeded, the cell group logic no longer exchanges energy with the rail line for charging or discharging the cell group connected therewith, and the voltage applied to the rail line is no longer used as reference voltage for the charging or discharging of the cell groups or the individual cells; that is, the supply line, by way of which the cell group is connected with the cell group logic, is definitely separated from the rail line. As a result, the charging or discharging of the group of cells is carried out by means of an unadulterated reference voltage and, during the data communication, the charging or discharging of the group of cells is interrupted in order to exclude a faulty charging or discharging.
The cell group logic is advantageously switched to active when a rail voltage is applied to the rail line which is above an enable voltage level situated below the maximal voltage level. The cell group logic is therefore advantageously constructed such that the voltage comparator unit switches the cell group logic to active when a rail voltage is applied to the rail line which is above an enable voltage level situated below the maximal voltage level. The central logic therefore advantageously has a control unit which drives the voltage converter unit to impress a rail voltage which is above an enable voltage level situated below the maximal voltage level in order to switch the cell group logic to active. In this advantageous embodiment, the cell group logics are compulsorily switched to passive, that is, disabled, in the event of a “short circuit to ground” fault. In this manner, a destruction of or damage to the individual cell groups is prevented.
According to the invention, the supply line of the cell group is advantageously connected such with the rail line that a power is transmitted between the latter which is situated at or above a first power level when the rail voltage is above the enable voltage level or a low voltage level situated above the enable voltage level and below a higher high-voltage level or the still higher maximal voltage level.
Also advantageously, the supply line of the cell group is connected according to the invention with the rail line in such a manner that a power is transmitted between the latter which is at or above a second power level situated above the first power level when a cell group voltage is above the enable voltage level and below the low voltage level or above the high voltage level and below the maximal voltage level.
According to the invention, the supply lines of different cell groups are advantageously connected such with the rail line that power is transmitted between the different cell groups and/or power is taken from the rail line or is fed to this rail line.
For this power transmission between the cell groups or at least one cell group and the rail line, the cell group logic according to the invention advantageously has a switch unit which is triggered by the voltage comparator unit and can connect the supply line of the cell group such with the rail line that a certain power is transmitted, in which case the voltage comparator unit determines the removal or feeding of energy from the rail line or to the rail line by means of defined voltage levels existing on the rail line and by means of a cell group voltage. In the case of the central logic according to the invention, the voltage control unit advantageously drives the voltage converter unit for this purpose to impress a rail voltage which is above the enable voltage level in order to drive the cell group logic to connect the supply lines of different cell groups such with the rail line that power is transmitted between the different cell groups and/or power is taken from the rail line or is fed to this rail line.
By means of these functions, a balancing of the cell voltages as well as the detecting of under- and overvoltages of individual cells can take place. In addition, the charging of the cells can be maintained in the standing operation, a charging and discharging or charge reversal between the individual cells can take place, and the individual cells can be diagnosed/monitored.
In the case of a unidirectional data communication between the central logic and the cell group logic(s), for example, an instruction to a defined cell group logic can take place by means of the central logic to connect the supply line of the connected cell group with the rail line, while simultaneously the other cell group logics are instructed to separate the supply lines of the respective cell groups from the rail line. In this case, a targeted charging as well as a targeted discharging of the cell group connected with the rail like can take place by way of the rail line. Since the central logic can determine the removal of energy from the rail line and the feeding of energy to the rail line respectively, it can in this case also carry out a targeted diagnosis of an individual cell group with respect to its voltage, its resistance and its capacitance. In the case of a bidirectional communication between the central logic and the cell group logic(s), such a diagnosis can also take place by the cell group logic(s), in which case the information transmission can be carried out by way of the bidirectional communication mechanism.
According to the invention, the data communication advantageously comprises the address, the command, the data, the safety and/or the response. Also advantageously, the data and/or the response comprise the internal resistance, the capacitance, the temperature and/or the voltage of a cell group. According to the invention, the data communication advantageously takes place by way of a binary coding, an amplitude coding, a pulse duration coding and/or an amplitude-pulse duration coding.
Advantageously, the control unit according to the invention drives the voltage converter unit to carry out the data communication between the cell group logic and the central logic by way of the rail line.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.